Microelectromechanical gyroscope with self-calibration function and method of calibrating a microelectromechanical gyroscope

• US 9,212,910 B2
• Filed: 10/09/2012
• Issued: 12/15/2015
• Est. Priority Date: 07/28/2011
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Donadel, Andrea, Ungaretti, Tommaso, Caminada, Carlo, Prandi, Luciano
• Primary Examiner(s): Macchiarolo, Peter
• Assistant Examiner(s): Jenkins, Jermaine
• Application Number:
  US13/648,215
• Publication Number:
  US 20130031950A1
• Time in Patent Office: 1,162 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G01C 19/5776 Signal processing not specific to any of the devices covered by groups G01C19/5607 - G01C19/5719

Abstract

A microelectromechanical gyroscope having a supporting structure; a mass capacitively coupled to the supporting structure and movable with a first degree of freedom and a second degree of freedom, in response to rotations of the supporting structure about an axis; driving components, for keeping the mass in oscillation according to the first degree of freedom; a read interface for detecting transduction signals indicating the capacitive coupling between the mass and the supporting structure; and capacitive compensation modules for modifying the capacitive coupling between the mass and the supporting structure. Calibration components detect systematic errors from the transduction signals and modify the capacitive compensation modules as a function of the transduction signals so as to attenuate the systematic errors.

Claims

1. A microelectromechanical gyroscope, comprising:

a supporting structure having first and second sensing terminals;

a capacitive coupling coupled to the sensing terminals;

a sensing mass coupled to the supporting structure through the capacitive coupling, the sensing mass being movable with respect to the supporting structure according to a first degree of freedom and being movable with respect to the supporting structure according to a second degree of freedom in response to rotations of the supporting structure about an axis;

driving components configured to maintain the sensing mass in oscillation according to the first degree of freedom;

a reading interface connected to the sensing terminals and configured to sense transduction signals indicative of the capacitance between the sensing mass and the supporting structure; and

first and second capacitive compensation modules connected to the first and second sensing terminals, respectively, and configured to compensate for a capacitance of the capacitive coupling between the sensing mass and the supporting structure, the first capacitive compensation module having a first variable capacitance coupled to the first sensing terminal, the second capacitive compensation module having a second variable capacitance coupled to the second sensing terminal, and the first and second variable capacitances being distinct from the capacitance of the capacitive coupling between the sensing mass and the supporting structure; and

calibration components coupled to the reading interface and configured to detect systematic errors from the transduction signals and to adjust the first and second variable capacitances of the first and second capacitive compensation modules as a function of the transduction signals to mitigate the systematic errors.

2. The gyroscope according to claim 1, further comprising a control unit configured to selectively activate and deactivate the driving components.

3. The gyroscope according to claim 2, wherein the calibration components include a signal processor configured to determine a compensation value as a function of the transduction signals and vary the first and second variable capacitances based on the compensation value.

4. The gyroscope according to claim 3, wherein:

the signal processor is configured to determine the compensation value as an offset compensation value in a first mode of operation during which the driving components are deactivated by the control unit;

the first and second capacitive compensation modules include first and second offset capacitive compensation modules, respectively; and

the control unit is configured to adjust the first and second offset capacitive compensation modules as a function of the offset compensation value.

5. The gyroscope according to claim 4, wherein:

the calibration components include a low-pass filter coupled to the reading interface, the low-pass filter being configured to receive the transduction signals from the reading interface and to provide filtered transduction signals; and

the processing module is configured to determine an offset compensation value based on the filtered transduction signals in a second mode of operation during which the driving components are activated by the control unit.

6. The gyroscope according to claim 4, wherein:

the signal processor is configured to determine a quadrature compensation value in a second mode of operation during which the driving components are activated by the control unit;

the first and second capacitive compensation modules include first and second quadrature capacitive compensation modules, respectively; and

the control unit is configured to adjust the first and second quadrature capacitive compensation modules as a function of the quadrature compensation value.

7. The gyroscope according to claim 6, wherein:

the driving components are configured to provide a main clock signal synchronous with oscillations of the sensing mass and a quadrature clock signal that is 90°

out of phase with respect to the main clock signal;

the calibration components include a demodulator configured to demodulate the transduction signals using the quadrature clock signal and to provide demodulated transduction signals; and

the signal processor is configured to determine the quadrature compensation value as a function of the demodulated transduction signals.

8. The gyroscope according to claim 7, wherein the demodulator is selectively connectable between the reading interface and the signal processor.

9. The gyroscope according to claim 1, further comprising a processing chain coupled to the reading interface, the processing chain being configured to generate output signals as a function of the transduction signals.

10. The gyroscope according to claim 9, wherein at least some of the calibration components are shared with the processing chain.

11. The gyroscope according to claim 9, wherein the calibration components are distinct from the processing chain.

12. The gyroscope according to claim 1, wherein:

the first capacitive compensation module includes plural first capacitors that are selectively connected to or disconnected from the first sensing terminal as a function of the transduction signals; and

the second capacitive compensation module includes plural second capacitors that are selectively connected to or disconnected from the second sensing terminal as a function of the transduction signals.

13. The gyroscope according to claim 1, wherein the calibration components include:

a demodulator configured to demodulate the transduction signals and to provide demodulated transduction signals;

a signal processor configured to determine an offset compensation value as a function of the transduction signals in a first operating mode and determine a quadrature compensation value as a function of the demodulated transduction signals in a second operating mode;

a first selector configured to electrically couple the demodulator to the reading interface during the second operating mode and electrically decouple the demodulator from the reading interface during the first operating mode; and

a second selector configured to electrically couple the demodulator to the signal processor during the second operating mode and electrically decouple the demodulator from the signal processor during the first operating mode.

14. An electronic system, comprising:

a control unit, and

a gyroscope coupled to the control unit, the gyroscope, including;

a supporting structure having first and second sensing terminals;

a capacitive coupling coupled to the sensing terminals;

a sensing mass coupled to the supporting structure through the capacitive coupling, the sensing mass being movable with respect to the supporting structure according to a first degree of freedom and being movable with respect to the supporting structure according to a second degree of freedom in response to rotations of the supporting structure about an axis;

driving components configured to maintain the sensing mass in oscillation according to the first degree of freedom;

a reading interface connected to the sensing terminals and configured to sense transduction signals indicative of the capacitance between the sensing mass and the supporting structure; and

first and second capacitive compensation modules connected to the first and second sensing terminals, respectively, and configured to compensate for a capacitance of the capacitive coupling between the sensing mass and the supporting structure, the first capacitive compensation module having a first variable capacitance coupled to the first sensing terminal, the second capacitive compensation module having a second variable capacitance coupled to the second sensing terminal, and the first and second variable capacitances being distinct from the capacitance of the capacitive coupling between the sensing mass and the supporting structure; and

calibration components coupled to the reading interface and configured to detect systematic errors from the transduction signals and to adjust the first and second variable capacitances of the first and second capacitive compensation modules as a function of the transduction signals to mitigate the systematic errors.

15. The system of claim 14, wherein the control unit is configured to selectively activate and deactivate the driving components.

16. The system of claim 14, wherein:

the calibration components include a signal processor configured to determine an offset compensation value as a function of the transduction signals in a first mode of operation;

the control unit is configured to deactivate the driving components during the first mode of operation;

the first and second capacitive compensation modules comprise first and second offset capacitive compensation modules, respectively; and

the control unit is configured to adjust the first and second offset capacitive compensation modules as a function of the offset compensation value.

17. The system of claim 16, wherein:

the signal processor is configured to determine a quadrature compensation value as a function of the transduction signals in a second mode of operation;

the control unit is configured to activate the driving components during the second mode of operation;

the first and second capacitive compensation modules include first and second quadrature capacitive compensation modules, respectively; and

the control unit is configured to adjust the first and second quadrature capacitive compensation modules as a function of the quadrature compensation value.

18. The system of claim 17, wherein:

the driving components are configured to provide a main clock signal synchronous with oscillations of the sensing mass and a quadrature clock signal that is 90°

out of phase with respect to the main clock signal;

the calibration components include a demodulator configured to demodulate the transduction signals using the quadrature clock signal and to provide demodulated transduction signals; and

the signal processor is configured to determine the quadrature compensation value as a function of the demodulated transduction signals.

19. The system of claim 16, wherein:

the calibration components include a low-pass filter coupled to the reading interface, the low-pass filter being configured to receive the transduction signals from the reading interface and to provide filtered transduction signals;

the signal processor is configured to determine an offset compensation value on the basis of the filtered transduction signals in a second mode of operation; and

the control unit is configured to activate the driving components during the second anode of operation.

20. The system according to claim 14, wherein:

the first capacitive compensation module includes plural first capacitors that are selectively connected to or disconnected from the first sensing terminal as a function of the transduction signals; and

the second capacitive compensation module includes plural second capacitors that are selectively connected to or disconnected from the second sensing terminal as a function of the transduction signals.

21. A method, comprising:

calibrating a microelectromechanical gyroscope, the calibrating including;

oscillating a sensing mass in a first degree of freedom with driving components;

sensing, through a reading interface, transduction signals indicative of capacitive coupling between the sensing mass and supporting structure, the sensing mass being movable with respect to the supporting structure according to the first degree of freedom and being movable with respect to the supporting structure according to a second degree of freedom in response to rotations of the supporting structure about an axis; and

compensating for a capacitance of the capacitive coupling between the sensing mass and the supporting structure, the compensating including;

detecting systematic errors from transduction signals; and

adjusting first and second variable capacitances of first and second capacitive compensation modules as a function of the transduction signals, so as to mitigate the systematic errors, the first and second variable capacitances being respectively coupled to first and second sensing terminal of the reading interface and being distinct from the capacitance of the capacitive coupling between the sensing mass and the supporting structure.

22. The method according to claim 21, wherein detecting systematic errors from the transduction signals includes deactivating the driving components during a first mode of operation, and sensing the transduction signals with the driving components deactivated.

23. The method according to claim 22, wherein detecting systematic errors from transduction signals includes:

activating the driving components and the transduction signals during a second mode of operation;

providing a main clock signal, synchronous with the oscillations of the sensing mass, and a quadrature clock signal, 90°

out of phase with respect to the main clock signal; and

demodulating the transduction signals using the quadrature clock signal.

24. The method according to claim 21, wherein the first capacitive compensation module includes plural first capacitors, the second capacitive compensation module includes plural second capacitors, and the adjusting includes selectively coupling the first and second capacitors to the reading interface as a function of the transduction signals.